Palladium-gold catalysts are known. They are used in acetoxylation. For instance, the oxidation of ethylene in the presence of a palladium-gold catalyst and acetic acid produces vinyl acetate, which is a useful monomer for the polymer industry.
Acetoxylation is commonly performed by the vapor phase reaction using supported palladium-gold catalyst. Methods for supporting palladium-gold catalysts are known. In general, the method involves depositing a mixture of palladium and gold salts onto a support and then reducing the palladium and gold to metals.
Palladium and gold are both precious metals. Therefore, many efforts have been made to increase the catalytic activity and reduce the amount of catalyst needed. For example, U.S. Pat. No. 6,022,823 teaches calcining the support impregnated with palladium and gold salts prior to reducing the metals. The catalyst shows improved activity.
One challenge still facing the industry is that the supported palladium-gold catalysts are often deactivated in acetoxylation. Thus, it is important to the industry to increase the activity stability of the supported palladium-gold catalysts. Ideally, the catalyst would have increased activity or productivity but would not incur increased cost.